1. Field of the Invention
The present invention relates to a crawler traveling apparatus for use mainly in a tractor and relates more particularly to a crawler traveling apparatus using a rubber crawler belt.
2. Description of the Related Art
Such crawler traveling apparatus using a rubber crawler belt is typically known from FIG. 6 of the Japanese Patent Application “Kokai” No.: Hei. 6-329059. In this, the crawler belt includes, in its inner peripheral face, a plurality of driving projections which engage with a drive wheel to be rotatably driven thereby. Further, these driving projections are guided from the right and left by a group of free wheels each comprising a pair of right and left free wheels. Each of the driving projections has a lateral face which is formed as a continuous inclined face extending with a uniform inclination along the entire height thereof. Whereas, an entire inner engaging face of each of the rotating wheels opposed to the driving projection is formed as an inclined face parallel with the lateral face of the driving projection.
With such crawler traveling apparatus described above, as described above the lateral face of the driving projection is provided as the inclined face having a uniform inclination over the entire height thereof and the inner lateral face of the ground free wheel is provided as the inclined face extending parallel to the lateral face of the driving projection. For this reason, when the crawler belt is laterally displaced due to a thrust applied thereto, the inner lateral face of the ground free wheel comes into contact with the entire lateral face of the driving projection, so that in a high-speed traveling, with relative rotational displacement between the lateral face of the driving projection and the inner lateral face of the ground free wheel there is generated a significant amount of friction heat, which tending to invite deterioration in the strength of the driving projection formed of rubber.
Further, in such operations as turn of the vehicle, slope traveling or a plowing operation when the vehicle travels with the one side of the crawler thereof being inclined and sunk in a plowed ground, there often happens an upper displacement of the ground free wheels relative to the crawler belt. In such case, a significant thrust load will be applied to an upper portion of the tapered driving projection, thus tending to invite deformation of the driving projection, thus resulting in durability deterioration.
Moreover, with such driving projection having right and left lateral faces having continuously uniform inclination, the ground free wheel tends to ride over the upper corner of the driving projection and to become “jammed” therewith. For instance, in the event of such riding of the ground free wheel, if the vehicle effects a traveling along a contour line (slope traveling) or rapid turn, there often occurs displacement in the layout of the driving projections as being deformed laterally of the belt. Then, as the driving projection becomes engaged with the ground free wheel under this condition, the ground free wheel tends to ride over the upper corner of the displaced driving projection, thus tending to invite the “jamming”. Also, when the crawler traveling apparatus comes in and out of a plowed groove, the ground free wheel will float off the crawler belt and then when the belt engages with a next driving projection, the jamming tends to occur due to the displacement of the driving projection. Moreover, when one lateral end of the crawler belt rides over a relatively small object such as a stone, a portion of the belt will be pushed up and deformed thereby to cause displacement of its driving projection. Then, when this displaced driving projection comes into engagement with the ground free wheel, the jamming phenomenon will again tend to occur.